Automatic circuit breaker



July 17, 1934. GUETT AUTOMATIC CIRCUIT BREAKER 2. Sheets-Sheet 1 FiledJan. 22, 1932 .5. uzaizw wmobm 531 lNVENTOR MONROE GUETT BY HIS ATTORNEYJuly 17, 1934. M. GUETT AUTOMATIC CIRCUIT. BREAKER Filed Jan. 22. 1932 2Sheets-Sheet 2 INVENTOR MONROE GUETT BY HIS ATTORNEYS Patented July 17,1934 PATENT OFFICE AUTOMATIC CIRCUIT BREAKER Monroe Guett, Hartford,Conn., assignor to The Arrow-Hart & Hegeman Electric Company, Hartford,Conn., a corporation of Connecticut Application January 22, 1932, SerialNo. 588,214

17 Claims.

This invention relates to circuit breakers which may be actuatedmanually at any time, or actuated automatically upon the occurrence ofpredetermined current conditions in the circuit which the circuitbreaker controls.

It is an object of my invention to make a circuit breaker of the abovetype which is reliable and quick in operation and in which the currentresponsive device is not under stress.

Another object is to make a circuit breaker of the above type in whichthe setting for tripping the circuit breaker may be accuratelymaintained.

Another object is to cut manufacturing costs of a circuit breaker of theabove type without the sacrifice of quality or reliability of operationof the device.

Another object is to make a circuit breaker which can be manufacturedmainly from stamped metal parts. 1

Another object is to provide protective means for current responsivedevices which are used to bring about the breaking of a circuit.

Another object is to provide a current responsive device for circuitbreakers which is protected against overheating upon the occurrence ofan excess current.

Another object is to provide a current responsive device for automaticcircuit breakers which device is provided with a shunt to carry theexcess current as soon as the device has responded to the excess currentsufficiently to trip the circuit breaker.

Other objects and advantages of my invention will become apparent as itis described in connection with the accompanying drawings.

In the drawings:--

Figure 1 is a side elevation view with part of the switch frame brokenaway to show the position of the parts when the circuit breaker isclosing the circuit.

Figure 2 is a view similar to Figure 1 but showing the parts of thecircuit breaker just after the breaker has been tripped.

Figure 3 is a view similar to Figure 1 but showing the parts in theposition they take just before the breaker has been manually snapped tocircuit breaking position.

Figure 4 is a view similar to Figure 1 but showthe thermally responsivemechanism and its guard removed.

Figure 7 is an end elevation of the thermally responsive mechanism andguard, which were removed for the purpose of making Figure 6.

This invention is an improvement of the invention described in myapplication Serial No. 500,- 352 filed December 5th, 1930, patented May30, 1933, No. 1,911,893.

Referring to the drawings the circuit breaker may be convenientlymounted upon a base 10 of insulating material having a pair of spacedstationary contacts 12 at one end which are adapted to be bridged by amovable bridging member 13 which carries contacts 14 to engage with thecon- 7 tacts 12. It is often desirable to mount the contacts 12resiliently to offset uneven wearing away of the contacts due. tofriction or the action of an electric arc as the device becomes worn.

The moving parts of the circuit breaking mech- 7 anism and the frame ofthe circuit breaker, whose functions and operations are about to bedescribed may (except for the springs) be made from sheet material,preferably metal, and given the desired or necessary shape and form bybending g0 and stamping operations. The irregular shape of the parts maybest be understood by reference to the drawings.

The moving parts of the circuit breaking mech anism are mounted betweenthe legs 16a of a frame 16, formed of a metal plate bent in U-form, thebase portion 16b of the frame being secured to the insulating base 10 byscrews. A manually movable member 20 provided with an insulating handle21 is pivotally mounted upon a pivot pin 22 which is located slightlyabove the base portion 16b of the frame and parallel to said baseportion. This manually movable member .20 is held approximately midwaybetween the legs 16a of the frame 16 by means of collars 24 upon thepivot pin 22. Also pivotally mounted upon the pivot pin 22 is anapproximately C-shaped member 26 which is automatically moved upontripping of the circuit breaker as will hereinafter be described. Thismember 26 lies next to the manually movable member 20 and is heldagainst movement axially of the pin 22 by the collars 24.

Two factors contribute to compel the member 26 to move with the manuallymovable member under normal conditions, that is to say during manualoperation of the circuit breaker. One factor is an arcuate latchingmember 30 which is mounted upon a pivot pin 32 located in the upperportion of the manually movable member 20 and passing through the centerportion of the latch ing member. The latching member 30 as viewed inFigures 1 to 4 is normally urged clockwise by means of a wire spring 31looped about the pivot pin 32 and engaging respectively with the handle21 and the latching member 30. Upon the latching member 30 there is anub 34 which engages with the handle 21 to prevent overthrow of thelatching member by the spring 31. The latching member is provided with ahooked nose 36 which engages with a complementary shoulder 38 on theupper or free end of member 26 and causes the member 26 to move with themanually movable member 20 as the member 20 is moved from off positionas shown in Figure 4 to on posi tion as shown in Figure 1.

The second factor, which causes the member 26 to move with member 20 isa still wire spring 50 coiled about one of the collars 24 and having itsopposite ends engaging, respectively, an outturned lug 52 at the lowerextremity of the member 26 on one side of the pivot 22, and an inturnedlug 54 on the lower part of the shank of the member 20 and on theopposite side of the spindle 22 from lug 52. moves member 20 from onposition to off position the lug 54 causes winding up of the spring 50and transmission of its power to lug 52 thus causing the member 26 tomove with member 20. The spring 50 and member 26 perform additional anddifferent functions during operation of the switch automatically, ashereinafter appears.

The movable bridging contact 13 is carried by a carrier member 40 whichis pivotally mounted upon a pair of fixedly located coaxial pins 42which pass through the legs 16a of the frame 16 and through side arms40a of the carrier. The movable contact is secured, in insulatedrelation, to the cross bar 40b of the carrier. side arms each have anextension 41 projecting at right angles to the arms in the direction ofthe base of the frame 16. By these extensions 41 the side arms of thecarrier become, substantially, bell crank levers. In order that theseextensions 41 will have plenty of room to pivot about the pins 42, thepins 42 are located in the frame legs 16b well above the pin 22.

Through the ends of the extensions 41 and connecting them a pin 46passes, and around it is anchored one end of a coil spring 48 whosefunction is to move the carrier with a snap action when its other end ismoved through dead center position as hereinafter described. Said otherend of the spring is looped about the upper or free end of the member26, adjacent the shoulder 38. This spring 48 may be considered as aprimary spring means since it is responsible for the snap movement ofthe movable contacts on actuation of the switch either automatically ormanually.

From the foregoing it may now be observed that as the manually movablemember 20 is pivoted about pin 22 from the position shown in Figure 1 tothe position shown in Figure 4, the spring 48 is carried past animaginary line between the pin 46 and the pivot pins 42. When the springreaches this imaginary line it is stressed and tends to rotate theextensions 41 about the pin 42 causing the movable bridging contact 13to be moved away from the fixed contacts 12 to open the circuit. Theprinciple involved in the action just described is well known in theelectric switch art and hence the manual operation of this device neednot be further described. In order to hold the movable contact incontact with the fixed contacts 12 until the spring 48 is stressed to amaximum, an inturned lug 56 is provided When the handle 21 Thecarriersupon a longitudinal extension 58 on one of the side arms 40a ofthe carrier 40. This lug engages with a complementary lug 60 which isturned out from the member 26. As the manually movable member is movedfrom the position shown in Figure 1 to that shown in Figure 4 the lug 60on the member 26 slides beneath and rubs against the edge of the lug 56upon the carrier 40 and prevents movement of the carrier until the lug60 passes from under the lug 56 on the carrier 40. The position of theparts just before the lug 60 passes from under the lug 56 is shown inFigure 3. When the circuit breaker is in this condition the spring 48 iswell stressed and the handle is almost in off position, only a slightfurther movement toward off" position being necessary to release thecarrier for snap action to circuit breaking position as shown in Figure4.

Just the opposite action takes place when the switch is moved from opento closed circuit position, i. e. from position of Figure 4 to theposition of Figure 1. In that operation the lug 60 slides overthe uppersurface of the lug 56 and holds the carrier 40 stationary until thehandle 21 is near the end of its travel from right to left (see Figure4), and then suddenly releases the carrier so that the spring 48, (bythat time in highly stressed condition) can move the carrier 40 andbridging contact 13 into closed circuit position (see Figure 1) with asnap.

In order that the switch may be operated automatically when an overloadoccurs in the circuit, I have provided a bimetallic device whichresponds to predetermined current conditions in the circuit by bendingand engaging with the latching member 30. This bimetallic devicecomprises a pair of parallel bimetallic strips 70 which are connected attheir tops by an integral bridge which is supplemented by a conductingplate 72 of high conductivity such for example as copper. To the lowerends of the bimetallic strips are riveted or otherwise secured terminalmembers 74, 75 and substantially rigid bars 76 of low resistance whichrun parallel to the bimetallic strips, but out of contact therewith.These bars 7 6 extend up to the upper end of the bimetallic stripsopposite the plate 72 and terminate there. Upon an excess currentpassing through the bimetallic strips they are bent by the heat of suchcurrent until the conducting plate 72 engages, as shown in Figure 2,with the bars which serve to shunt the current around the bimetallicelement, thus relieving it of the excess current burden and furthereffort to distort.

Passing through the free end of the bimetallic element is an adjustingbolt 78 which engages with the latching lever 30 when the bimetallicelement is bent to a predetermined degree as shown in Figure 2. Thisbolt makes possible setting of the breaker to trip on different degreesof overload. When the bimetallic element is bent as shown in Figure 2,the latching lever 30 is caused to pivot about the pin 32 disengagingthe shoulder 36 from the shoulder 38. Then spring 50, which is-normallyrestrained by latching member 30, is free to act and carries the upperend of the member 26, in clockwise direction, as shown in Figure 1,about pivot pin 22 thus. carrying spring 48 through dead centerposition. As soon as this movement has proceeded far enough to move thelug 60 on member 26 from under lug 58 on the carrier, then the action ofspring 48 will be exerted on the carrier to cause disengagement of theswitch contacts.

It will thus be seen that the spring 50 is in es- 150 sence asecondaryspring means since it is active only upon tripping of thecircuit breaker and then only to cause the primary spring 48 to causethe actual contact movement.

To reset the switch the handle must be moved to oil position permittingthe latch member 30 to engage with the member 26 again. Then the, switchis ready for manual operation once more. It will be observed that incase the conditions in the circuit which impose the excess current havenot changed that the current responsive device will again move thelatching member 30 and trip the switch. It is impossible to hold thecircuit breaker in the on position by means of holding the handle in onposition, for the reason thatthe tripping of the circuit breaker isindependent of the handle.

It will be observed that the circuit breaker could be tripped byelectromagnetic means or any other current responsive device, as well asby the thermal device shown and that this thermal device may be used inconnection with other circuit breakers. Obviously many changes andmodifications may be made within the scope of my invention and thereforeI do not limit the invention to the specific embodiment shown in thedrawings.

I claim:

1. An electric switch comprising fixed and movable contacts, manuallyoperable means to move said movable contact, a carrier for said movablecontact, primary spring means actuable by said manually operable meansto move said carrier with a snap, and secondary spring means releasableupon overload to move said primary spring means and thereby cause saidprimary spring means to move said movable contact, and a latchingmembernormally restraining said secondary spring means, in combination with apair of bimetallic current carrying members electrically connected atone end, a pair of low resistance bars connected to the other ends ofsaid bimetallic members, conducting means adapted to engage said bars,when said bimetallic members move to trip said latch, to shunt thecurrent around said bimetallic members.

2. An electric switch comprising fixed and movable contacts, manuallyoperable means to move said movable contact, a carrier for said movablecontact, primary spring means actuable by said manually operable meansto move said carrier with a snap, and secondary spring means releasedfor operation upon overload to move said primary spring means andthereby cause said primary spring means to move said movable contact.

3. An electric switch comprising fixed and movable contacts, manuallyoperable means to move said movable contact, movable contact carryingmeans pivotally mounted about a fixed axis, primary spring meansactuable by said manually operable means to move said carrier with asnap, and secondary spring means released for operation upon overload tomove said primary means and thereby cause said primary spring means towith a snap, and spring pressed auxiliary means for moving said primaryspring means and said carrier, said auxiliary means being normallyrestrained but releasable upon overload.

5. An electric switch comprising fixed and movable contacts, manuallyoperable means to move said movable contact, a carrier for said movablecontact, primary spring means actuable by said manually operable meansto move said carrier with a snap, and spring pressed auxiliary means formoving said primary spring means and said carrier, said auxiliary meansbeing pivotally mounted abouta fixed axis and being normally restrainedbut releasable upon overload.

6. An electric switch comprising fixed and movable contacts, manuallyoperable means to move said movable contact, a carrier for said movablecontact, primary spring means actuable by said manually operable meansto move said carrier with a snap, and spring pressed auxiliary means formoving said primary spring means and said carrier, said auxiliary meansbeing normally restrained but releasable upon overload, and saidmanually operable means and said auxiliary means being pivotally mountedabout the same fixed axis.

7. An electric switch comprising fixed and movable contacts, manuallyoperable means to move said movable contact, movable contact carryingmeans pivotally mounted about a fixed axis, primary spring meansactuable by said manually operable means to move saidmovable-contactcarrying means with a snap, and a spring-pressedauxiliary means for moving said primary spring means and saidmovable-contact-carrying means, and said manually operable means andsaid auxiliary means being pivotally mounted about the same fixed axis.

8. An electric switch comprising fixed and movable contacts,movable-contact-carrying means,

spring means, manually movable means, springpressed means pivoted abouta fixed axis and normally movable with said manually movable means tocarry said spring means through dead center position to actuate saidmovable contact with a snap, said spring-pressed means being releasedupon overload to carry said spring means through dead center positionindependent of said manually movable means, said spring-pressed meansand said manually movable means being pivotally mounted about the samefixed axis.

10. An electric switch comprising fixed and movable contacts, movablecontact carrying means, spring means, manually movable means,spring-pressed means pivoted about a fixed axis, and normally movablewith said normally movable means to carry said spring means through deadcenter position to actuate said movable contact with a snap, a latchnormally holding said spring-pressed means for movement with saidmanually movable means, means to trip said latch upon overload torelease said spring-pressed means, said spring-pressed means uponrelease, carrying said spring means through dead center position toactuate said movable contacts.

11. An electric switch comprising fixed and movable contacts, a manuallymovable member pivoted about a fixed axis, an auxiliary member ill alsopivoted about said axis and normally movable with said manually movablemember, a carrier for said movable contacts, primary spring meansmovable through a dead center position to actuate said movable contactwith a snap, secondary spring means urging said auxiliary member in onedirection, said secondary spring means being normally restrained butbeing released upon overload causing said auxiliary member to carry saidprimary spring means through dead center position.

12. A current responsive device comprising a plurality of low resistancemetallic bars, bimetallic current carrying members secured to one end ofsaid bars, conducting means bridging the other ends of said members,adapted to engage said bars when said members are distorted by heat' ofan excess current.

13. A current responsive device comprising a pair of parallel bimetalliccurrent carrying members, conducting means bridging said members at oneend, a pair of low resistance bars secured to the other ends of saidmembers and extending alongside of them, said conducting means beingadapted to engage said bars, when said members are distorted by heat, toshunt current around said members.

14. In an electric switch, a manually movable member, a switchingmember, spring means movable through dead center by said manually movable member to cause movement of said switching member with a snap, andmeans engaging during a portion of the movement of said manual member toprevent snappingof said switching member until said spring is well pastdead center.

15. In an electric switch, a manually movable member, a switchingmember, spring means movable through dead center by said manuallymovable member to cause movement of said switching member with a. snap,and means engaging prior to said spring means coming into dead centerposition and continuing for a substantial portion of the movementthereafter but finally releasing said switching member for snappingmovement.

16. In an electric switch, a pivotally mounted manually movable member,a pivoted switching member, spring means movable through dead center bysaid manually movable member to cause movement of said switching memberwith a snap, and means engaging during a portion of the movement of saidmanual member to prevent snapping of said switching member until saidspring is well past dead center.

17. In an electric switch, a manually movable member, a switchingmember, spring means movable through dead center by said manuallymovable member to cause movement of said switching member with a snap,and means on said manually movable member cooperating with means on saidswitching member to hold said switching member against movement as saidspring is moved through dead center position and for a substantialmovement thereafter but finally releasing said switching member forsnapping movement.

MONROE GUETT.

